Here i'm using script taken from somebody. it could be a safari upload progress plugin, but it won't. safari is just too slow. use google chrome.
The idea is to send POST-html5 request and then replace content by request response. It is important keep response javascript running and watch headers. For example, what you will do if you receive 301 after html5-post? [redirect, ya?]

What to do?
1. Generate unique form ids and apply html5-post to all forms on page.
2. Create safari statusbar with upload progress.
3. Add some code for headers operation.
4. Publish in safari extensions on apple site.

Your browser does not support Ajax uploads :-(The form will be submitted as normal.